Long lines formed at blood donation centers across the US after the Orlando terror attack that left dozens dead.
Photograph: Gerardo Mora/Getty Images

HIV experts and LGBT advocates across the country are calling on the US government to end its “discriminatory” ban on blood donations from gay men, with a renewed policy push emerging from the mass shooting that killed 49 people at a gay nightclub in Orlando.

Some advocates hope the harsh reality in Orlando – that gay men can’t donate blood to support those suffering from one of the worst attacks on LGBT people in American history – will push lawmakers and the FDA to end its ban altogether.

On Tuesday, which was World Blood Donor Day, a group of Democratic lawmakers sent a letter to the FDA noting that there is a dire need for blood in Orlando and urging federal officials to eliminate the 12-month regulation.

Supporters pushing for reform argue that the FDA could end its restrictions without legislation.

Scott Wiener, a supervisor in San Francisco who is gay and who has criticized the restrictions, said the time was right to enact reforms.

“It adds insult to injury. Here we have someone who murders 50 of our brothers and sisters, and then our own government turns around and says we’re not allowed to help them simply because we’re gay,” he said Tuesday. “There is no basis in science for this ban, and that is pure and simple discrimination.”

Despite the call from some in Congress for federal officials to “swiftly” end the ban and establish a “less discriminatory system”, the FDA on Tuesday said that it had no plans to change its policy.

“The FDA has examined the possibility of eliminating all deferrals for HIV and simply relying on testing of donated blood or reducing the deferral window; however, scientifically robust data are not available to show that this would not lead to decreased safety of the blood supply,” the agency said in a statement to the Guardian.

“Therefore, deferral policies continue to have an important role in ensuring the safety of the blood supply.”

The statement said the FDA would reevaluate its policies “as new scientific information becomes available”.

In the wake of the deadliest US mass shooting in modern history, which also left more than 50 people injured on Sunday, local blood banks in Florida issued urgent calls for donations. But gay men who wanted to donate blood to people recovering from the attack at Pulse nightclub were unable to offer their support.

That’s because the FDA bans men who have had sex with men in the previous 12 months from donating blood – despite repeated testimony from medical experts arguing that the restriction is not supported by scientific evidence.

“This really is an important moment, and we need to call it what it is, which is an irrational ban,” said Paul Volberding, director of the Aids Research Institute at the University of California at San Francisco. “This is based on fear and stigma, and there’s no other way to see it.”

But Hyman Scott, research scientist with Bridge HIV, a program of the San Francisco department of public health, said there are no studies showing that shorter bans or no bans would increase donations of HIV-infected blood. “The tools we have available don’t support that the one-year ban is necessary.”

But LGBT activists have argued that the one-year waiting period is effectively a ban on queer men and is a discriminatory rule that continues to unnecessarily block a huge segment of the population from giving blood without any public health justification.

Testing technology has improved dramatically since the donation restrictions emerged in 1983 during the HIV/Aids epidemic, and experts contend that HIV-positive donors can now be screened out. The American Medical Association argues that the deferral periods should be rooted in science and that the government should consistently apply the rules based on donors’ risk factors – not their sexual orientation.

Argentina ended its ban on gay and bisexual men donating blood last year, and Italy has also transitioned away from a total ban on gay men, instead assessing individuals based on risk. The UK and Australia have similar policies as the US, with 12-month deferrals.

For some LGBT people who were eager to donate blood, the ban has exacerbated the trauma of the violence at Pulse that resulted in the deaths of dozens of queer people and Latinos.

“This was a very important and tangible way we could go and support other members of the community,” said Jeff Sheehy, an HIV advocate on the board of the California Institute for Regenerative Medicine.

“To be denied that by an outdated rule that’s really based more on prejudice than science at this point is hurtful … It reminds us that in many ways, our civil rights are still not fully recognized throughout the country.”